Vehicle occupant detection systems are useful in connection with air bags and other pyrotechnically deployed restraints as a means of judging whether, and how forcefully, to deploy the restraint. One fundamental parameter in this regard is the weight of the occupant, as weight may be used as a criteria to distinguish between an adult and an infant or small child.
One prior weight estimation technique is to install an array of variable resistance pressure sensitive elements in the seat, and to sum the individual pressures to determine occupant weight. A restraint system based on this technique is shown and described in the U.S. Pat. No. 5,474,327, issued on Dec. 12, 1995, and assigned to the assignee of the present invention. In practice, however, such systems tend to be relatively costly to implement, and require a significant amount of signal processing for proper calibration and weight estimation.
Another possible technique is to instrument the seat frame with strain detectors, for example. However, this technique is also costly to implement, and cannot be readily applied to existing seat structures not designed for strain sensing.
Accordingly, a simple weight estimation apparatus is desired. Ideally, the apparatus would be easy to install in existing seat designs, and would require a minimum amount of processing to arrive at a weight estimation sufficiently accurate to enable occupant-appropriate restraint deployment decisions.